in-band: Generalize the in-band code to arbitrary (IP,port) pairs.

in-band: Generalize the in-band code to arbitrary (IP,port) pairs.

Until now the in-band code has taken an rconn (recently, multiple rconns)
and used its remote IP address as the one for which to set up flows.  But
we also need to support in-band control to the OVSDB manager, and OVSDB
does not use rconns.  This commit takes the first step toward this support
by generalizing the in-band code to take an arbitrary number of (IP,port)
pairs as remotes for which to set up flows.